I just read about Google’s Canonical Link Tag. It’s a little application of RDFa’s “rel” property. It is not a big thing, but I’m happy it is from Google, who seems quite remote from semantic web technologies.
“Last week Google, Yahoo, and Microsoft announced support for a new link element to clean up duplicate urls on sites. The syntax is pretty simple: An ugly url such as http://www.example.com/page.html?sid=asdf314159265 can specify in the HEAD part of the document the following: That tells search engines that the preferred location of this url (the “canonical” location, in search engine speak) is http://example.com/page.html instead of http://www.example.com/page.html?sid=asdf314159265 .”